1. Field of the Invention
This invention relates to a device which receives and decodes digital broadcasts, and in particular, to processing performed when undecoded video data and audio data are input from an external recording/playback device.
It also relates to a device which records and plays back video signals and audio signals coded using a high performance technique such as that of MPEG (Moving Picture Image Coding Experts Group), and in particular, to a technique whereby identifying data is added showing a discontinuity or speed change playback mode of a playback program.
2. Description of Related Art
In recent years, in the U.S.A. and Europe, systems have become generalized where high performance coding techniques such as developed by MPEG (Moving Picture Image Coding Expert Group) are applied to the coding of video signals and audio signals, which are then transmitted via a communications satellite and decoded on the receiving side.
In these systems, a special receiver/demodulator is required on the receiving side. This receiver comprises a part which selects a transport stream corresponding to a desired channel from a transport stream in which the data from a plurality of channels is multiplexed, a part which separates desired program video and audio data from the desired channel transport stream, and a part which decodes the separated video and audio data.
In these systems, to make it possible for the receiver/decoder to receive the desired channel transport stream and separate the desired program video and audio data, PSI (Program Specific Information), EPG (Electronic Program Guide) or SI (Service Information) is added to the multiplexed transport stream.
Video tape recorders (referred to hereafter as DVCR) which encode video and audio signals before recording or playing them back, have been proposed. The concept has also been proposed of recording/playing back this digital broadcast video data and audio data on such a DVCR without decoding them (xe2x80x9cDigital Video Reader, illust.xe2x80x9d, pp. 140-152, Ohm Co., Aug. 25, 1995, ed. by Yukio Kubota).
This invention aims to make it possible to perform rapid decoding of video data and audio data in a receiver/demodulator if there is a program change when a DVCR of the aforesaid type continuously plays back a plurality of digital broadcast programs, and this data is then input to such a receiver/demodulator.
This invention further aims to provide a digital signal recording/playback device and digital signal playback method wherein there is no break in video data and audio data when the output during speed change playback of such a DVCR is input to a receiver/demodulator and decoded.
To resolve the above problems, the digital signal processor according to this invention is characterized in comprising first means for selecting a transport stream corresponding to any channel from a transport stream containing a plurality of multiplexed channels, second means for separating video data and audio data in any desired program from this transport stream by referring to supplementary data in the selected transport stream, third means for decoding the separated video and audio data, fourth means for sending video data, audio data and supplementary data from external devices to the second means, and detecting data indicating a program discontinuity, and fifth means for initializing the third means when the fourth means detects data indicating a program discontinuity.
Further, the digital signal processing method according to this invention is characterized in that, in a digital signal processor comprising first means for selecting a transport stream corresponding to any channel from a transport stream containing a plurality of multiplexed channels, second means for separating video data and audio data in any desired program from the transport stream by referring to supplementary data in the selected transport stream, third means for decoding the separated video and audio data, and fourth means for sending video data, audio data and supplementary data from external devices to the second means, and detecting data indicating a program discontinuity, the third means is initialized when the fourth means detects data indicating a program discontinuity.
According to this invention, the third means is initialized when the fourth means detects data indicating a program discontinuity.
Further, the digital signal recording/playback device according to this invention comprises first means for inputting/outputting a digital signal coded by a predetermined coding scheme, second means for recording said digital signal transmitted by said first means in a recording medium, third means for reproducing said digital signal recorded on said recording medium, and fourth means for detecting a program change in said digital signal played back by said third means, and is characterized in that said fourth means adds a first identifying data to the digital signal output by said first means when a program change is detected.
Further, the digital signal playback method according to this invention is characterized in that a first identifying data is added to this digital signal when a program in a playback digital signal changes, when a digital signal coded by a predetermined coding scheme is played back from a recording medium and output to an external device.
In the digital signal recording/playback device and digital signal playback method according to this invention, a second identifying signal may further be added during speed change playback.
According to this invention, a fourth means adds the first identifying data to the digital signal output by the first means when a program change in a digital signal played back by a third means is detected.
According to this invention, as described in detail hereinabove, decoding of video data and audio data can be performed rapidly when a program input from an external device is changed.
Also, as described hereinabove, decoding can be rapidly performed when there is a program change when playback data is input to and decoded by the receiver/demodulator according to this invention. Further, when the output from speed change playback is input to the receiver/demodulator, breaks in the decoded video data and audio data output can be avoided.